Explosive compositions containing ammonium nitrate



July 31, 1962 w. E. GORDON 3,046,888

EXPLOSIVE Con/[POSITIONS CONTAINING AMMONIUM NITRATE Original Filed June 16, 1958 ATTORNEY llnited grate-s Patent if@ In the present invention relates to explosive compositions and their use in blasting systems. More particularly, the invention relates to explosive compositions including ammonium nitrate prills and liquid hydrocarbons.

The present application is a division of my copending application Serial No. 742,279, led lune 16, 1958, entitled Explosive Compositions Containing Ammonium Nitrate, now abandoned, which in turn is a continuationin-part of my application Serial No. 698,069, filed November 22, 1957, entitled Treatment of Ammonium Nitrate Prills and Explosive Compositions, now abandoned.

The principal object of this invention is to provide an inexpensive explosive composition which does not exhibit explosive properties in the usual hazard determinations, yet is sensitive to detonation by means of ordinary high velocity detonating fuse and has potential explosive power comparable to conventional fixed explosives.

Another object of this invention is to provide an inexpensive explosive composition consisting essentially of ammonium nitrate prills having inhibited caking tendencies and 0.5 to 8 percent of liquid hydrocarbons.

Ammonium nitrate has long been employed in explosive compositions but usually in admixture with a fixed explosive such as gelatin dynamite. Recently it has been discovered that ammonium nitrate in the form of spherical 3 Claims.

' prills can be admixed with a hydrocarbon fuel oil and employed as a bulk explosive composition. The compositions have been relatively insensitive and have required a substantial primer charge for detonation, usually dynamite or other fixed explosive.

Such compositions can be detonated satisfactorily and reliably without fixed explosive primer charges where the ammonium nitrate prills are uncoated and the oil content is carefully controlled. It has been the practice of the ammonium nitrate indus-try to provide a coating of powdered clay or diatomaceous earth over the surfaces of the ammonium nitrate prills prior to transportation and storage. The clay-coating prevents caking of the prills and permits their storage in a free-flowing condition. In the principal use of ammonium nitrate prills as an agricultural fertilizer, the presence of clay-coating has not been disadvantageous. The clay-coating normally provided by ammonium nitrate manufacturers varies from about 2 through 5 -percent by weight of the ammonium nitrate prills. The conventional clay'coating, however, has deleteriously affected the properties of ammonium nitrate prills as an explosive ingredient. f

The clay-coating diminishes the available power released from resulting explosive compositions. The claycoating severely diminishes the sensitivity of the resulting compositions and consequently necessitates use of fixed explosive primer charges for detonation. The clay-coating interferes with the detonation propagation of a charge of the resulting composition; consequently charges of the explosive frequently are incompletely detonated when the explosive flame front dies out in the charge. These failings of the available clay-coated ammonium nitrate-fuel oil explosives have been compensated to date (l) by the inclusion of fixed explosives in the composition, (2) by providing a substantial primer charge of fixed explosive, and (3) by providing a plurality of fixedexplosive primer itl@ charges at spaced distances throughout the explosive column.

Ammonium nitrate exhibits `a cake forming tendency as a consequence of its peculiar transition in crystalline structure which occurs at about 32 C. Uncoated ammonium nitrate particles, undergoing crystalline transition, tend to coalesce and to form large caked masses of ammonium nitrate. Caked masses of prill must tbe crushed before the ammonium nitrate can be admixed with fuel oil to prepare explosive compositions. The crushing is ldisadvantageous since it introduces a spectrum of particle sizes in the crushed product. Explosive eicacy is known tot increase with uniformity of particle sizes, and conversely, to decrease when a spectrum of particle sizes exists. Hence, some form of anti-caking treatment for the ammonium nitrate prills is desirable to maintain their free-owing, relatively uniform particle size constitution.

One known caking inhibition treatment for ammonium nitrate involves a surface treatment With various dyestus such as acid magenta. U.S. Patent 2,720,446. Such treatments are different in kind from dusting the prills with powdered solid-s. Powdered solids coatings interfere with the sensitivity, available power and explosive propagation properties of the compositions with liquid hydrocarbons.

I have found that the quantity of clay-coating customarily employed in ammonium nitrate prills by manufacturers is more than required to effect caking inhibition. Adequate caking inhibition can be achieved by providing a surface coating on the ammonium nitrate prills of about 0.25 weight percent of finely divided inert solid particles such as clay, diatomaceous earth, dehydrated silica gel, silicates, gum and the like. The presence of linely divided inert solid particles as a surface coating on the ammonium nitrate prills does not seriously interfere with the sensitivity or available power of compositions provided that the quantity is less than about 0.6 percent by weight. The presence of about 0.1 weight percent coating provides some caking inhibition.

Thus by employing ammonium nitrate prills having from about 0:1 to about 0.6 percent by weight of a surface coating of finely divided inert solid particles, I have developed an explosive composition comprising coated arnmonium nitrate prills and liquid hydrocarbons which is adequately inhibited against caking tendencies, yet retains sensitivity to detonation by means of high velocity detonating fuse alone, retains virtually all of the potential power available in explosive compositions prepared from uncoated ammonium nitrate prills, and possesses suitable explosion propagation properties.

According to the present invention, ammonium nitrate prills are provided with a surface coating of 0.1 to 0.6 percent byweight of finely divided inert solid particles such as clay, diatomaceous earth, dehydrated silica gel, silicates, gum and the like. The surface coating may be applied to the ammonium nitrate prills by tumbling the prills in a rotary drum together with a measured quantity of the finely divided inert solid particles. Other coating techniques are known in the art. U.S. 2,644,769. Perferably, the inert coating of finely divided solid particles on the ammonium nitrate prills comprises about 0.25 to 0.4 percent by weight of the prills. Thus coated, the prills can be transported and stored for extended periods without experiencing severe caking which would require comminution. Surface treated prills can be homogeneously adrnixed with from 0.5 to 8 percent by weight of liquid hydrocarbons such as fuel oil, to prepare an explosive composition.

' In a preferred embodiment, two explosive compositions 4are prepared from the coated prills. The first composi- Such compositions possess sensitivity and are detonatable by means of ordinary high velocity detonating fuse or explosive caps. Hereinafter such compositions are referred to as sensitive compositions. A second explosive composition is prepared containing from about 4 to .about 8 percent by weight of liquid hydrocarbons, preferably about 6 percent. Such explosive compositions possess a maximum power release and are detonatable in response to the detonation of the above described sensitive compositions. Hereinafter, the compositions having from about 4 to about 8 percent liquid hydrocarbons are referred to as power compositions. Either of the two compositions can be detonated by means of ordinary detonating fuse alone. Occasional misfires may result where an explosive charge consists of the power corn.- positions alone.

Ammonium nitrate prills are commercially available as uniformly sized spheres from about 0.05 to 0.15 inch in diameter. The prills sometimes have a non-porous composition and a glassy appearance. Such prills are unsuitable as explosive ingredients because of their difficulty in absorbing liquid hydrocarbons. somewhat porous prills which have a non-lustrous appearance and which are quite friable. The preferred prills can be easily crushed between nger and thumb.

In my 1coperfding application 698,069, supra, limitations were set forth to define certain types of coating agents for providing caking-inhibition over Ithe surfaces of `'ammonium nitrate prills. The coating agents described therein possessed large surface area to provide oil-absorbing material on the surfaces of the prills which would prevent drainage of oil from the prills. It had been found that an oil drainage phenomenon occurred With some prills which allowed the oil to separate from the prills before homogeneous absorption into the prills. On reviewing that phenomenon, it appears that glassy, relatively non-porous prills were the malefactors. When non-lustrous, somewhat porous prills are employed, the oil drainage phenomenon becomes negligible.

The hydrocarbons may be of any chemical characterization, to wit, parafiinic, olefinic, naphthenic, aromatic, saturated or unsaturated. Hydrocarbons which are highly viscous at atmospheric temperatures can be heated to promote fluid-ity for preparing compositions. A preferred hydrocarbon is No. '2 fuel oil which is readily available commercially and is relatively inexpensive.

The inert solid particles employed las a coating material for the ammonium nitrate prills should be in powdered form to provide a very thin coating over the relatively large prills. Powdered clay, diatomaceous earth, dehydrated silica gel, calcium silicates, silica-alurnina, gums and similar inexpensive inert materials may be selected. A variety of inert solids have been employed in the ammonium nitrate industry to inhibit caking tendencies. Any of those finely divided inert solids possess the properties herein reported. Blast furnace ily ash has been found to be suitable. Other suitable materials include kaolin, fullers earth, chalk, kieselguhr, bentonite, cellulose derivatives, powderd carbonaceous ingredients such as carbon black, sawdust, resins, coal and the like.

For a full understanding of the present invention, its objects and advantages, reference should be had to the accompanying detailed description and illustrations in which:

FIGURE 1 is a graphical illustration relating the detonation sensitivity of ammonium nitrate and oil mixtures with the concentration of finely divided inert solid anti-caking ingredients at varying oil concentrations;

FIGURE 2 is a graphical illustration representing the explosive power of compositions of ammonium nitrate and fuel oil for uncoated prills yand for coated prills according to the present invention; and

FIGURE 3 is a schematic illustration in cross-section of a blast hole illustrating a preferred embodiment of the present invention.

It is preferred to use CTI Explosive Sensitivity The detonation sensitivity of explosive compositions according Ato the present invention is illustrated in FIGURE l. To develop the relationships shown in FIGURE 1, a number of cardboard cylinders of -ammonium nitrate and fuel oil compositions were prepared with varying oil concentrations and Varying quantities of surface coating on the ammonium nitrate prills. Each of the individual cardboard cylinders was armed by wrapping about its circumference a length of high velocity det-onating fuse. Commercially available fuses having 40-grains per foot, 50grains per foot, 60-grains per foot, 1GO-grains per -foot and l-grains per foot were employed in these determinations.

Detonating fuses are cord-like materials containing a high velocity fixed explosive core covered with fabric. Thefixed explosive core usually is pentaerythritol tetranitrate (PETN) on cyclonite (RDX). The detonating fuses are rated according to the number of grains of fixed explosive contained in each foot of length. Thus, 40- grain detonating fuse contains 40 grains of fixed explosive per foot of length.

A suflicient number of explosive charges at each oil concentration and composition was tested with varying weights of detonating fuse to permit statistical determination of a grain weight per foot of charge circumference which would result in a 50 percent reliable detonation of the specific charge-that is, the weight of fuse which will detonate the specific charge in 50 percent of the tests. The more sensitive explosive compositions can be detonated with lower weights of fuse. As expected, the 2 percent oil compositions Iwere the most sensitive and the 6 percent oil compositions were least sensitive. Four percent oil compositions were intermediate. These principles have been taught by S. R. Brinkley, Jr., and C. von Elbe and described in copending application S.N. 667,141, filed .lune 2l, 1957, entitled Explosive Compositions Containing Ammonium Nitrate, now abandoned.

Referring to FIGURE l, it can be seen that the sensitivity of the explosive compositions decreases as the quantity of finely divided inert solid particulate surface coating material increases. The sensitivity ldecrease is not appreciable below 'about 0.6 percent of inept solids. Thus, the detonation sensitivity of the sensitive compositions (Curve C) is only slightly decreased by the provision of caking inhibition according to the present invention. Note that the detonation `sensitivity of the power compositions (curve A) is severely raffected by the addition of a caking inhibiting surface coating in excess of about 0.4 percent by weight. Decreased sensitivity is accompanied Yby a decreased ability of the composition to propagate an explosion throughout a column of explosive charge. Intermediate compositions (curve B) exhibited intermediate sensitivity decreases.

Explosive Power Referring to FIGURE 2, available explosive power from explosive compositions is illustrated as a function of the oil percentage in the composition. The relationship is shown for both uncoated prills and for the coated prills of this invention. The data for developing the curves of FIGURE 2 were obtained by confining charges of test compositions in the bore of a steel block having a six-inch outer diameter and a one-inch bore. The explosive charges were detonated with a Tetryl booster charge. The expansion of the block bore was measured to determine relative explosive power. The expansion of the test block in mils is plotted in FIGURE 2 against the oil percentage for both uncoated prills and for the coated prills of this invention. The coated prills contain 0.4 percent by weight of finely divided inert solid particles of synthetic calcium silicate as a surface coating. The liquid hydrocarbon in all instances was No. 2 fuel oil.

Caking Inhibition To illustrate the efficacy of caking inhibition resulting from the powdered solids surface coating described herein, comparative tests were conducted. Four samples were employed in the tests. Samples A rand B consisted of uncoated ammonium nitrate prills. Samples C and D were the same prills coated with 0.4 percent by weight of powdered clay. Samples A and C were placed in sealed containers; samples B and D were placed in open containers. The four samples were placed in an oven and maintained at 100 C. for 24 |hours, thereafter cooled below the crystalline transition temperature of 31 C. for 24 hours. 'Ihe heating a-nd cooling cycle was repeated several times. The uncoated prills of samples A and B formed solid calced masses. The surface coated prills of samples C and D remained free-flowing and uncaked.

Safety Features Samples of explosive compositions prepared according to the present invention were subjected to Va; series f standard explosive tests including (A) Drop-weight Impact test (B) Friction Impact test (C) Static Electricity test (D) Thermal Sensitivity test These standard test methods are described in U.S. Bureau of Mines Bulletin 346 (1931), Physical Testing of Explosives, by C. E. Monroe and I. E. Tiffany.

Ammonium nitrate prills coated with 0.3 percent by weight of inely divided synthetic calcium silicate were employed as the starting material. The coated prills were homogeneously admixed in two batches with 2 percent and 6 percent by weight of No. 2 fuel oil. The 2 percent batch in the sensitive" composition and the 6 percent batch in the power composition are herein described.

(A) Drop-weight impact test- A standard dropweight impact test machine was employed. The machine has a -kilogram weight which can be raised 300 centimetersabove the test sample and allowed to fall onto the sample. In ten testseach, neither sample detonated when the weight was dropped from the top of the machine onto the sample. Commercial dynamite will detonate in the same machine when the weight is dropped from a height of 60 centimeters. TNT detonates in the same machine when the weight is dropped from a height of 120 centimeters. Hence the present explosive composition is so insensitive to impact detonation by this standard test that it can safely be transported without the usual extreme explosive precautions.

(B) Friction impact test.-In this standard test, a sample of explosive composition is placed on a grooved steel surface and scraped by a swinging steel shoe for at least seventeen swings. YEach of the two compositions was tested ten times (seventeen swings in each test) without detonation. Some commercial dynamites will detonate in this test. Normally TNT will not detonate in this test.

(C) Static electricity test-No detonation'of either explosive composition resulted when subjected to a standard static 500G-volt electrical discharge. normally will not detonate in this test. Some commercial dynamites, depending upon their state of subdivision, will detonate in this test.

(D) Thermal sensitivity test. Approximately one gram of the explosive composition is heated in a glass test tube placed in an oil bath which is heated at a constant rate. The two samples of the present composition were heated from room temperature to about 415 F. Melting occurred at 337 to 345 F. As heating continued above 415 F., the temperature of the samples rose faster than that of the controlled-heat oil bath, indicating that exothermic autodecomposition was occurring. Detonation did not occur although a maximum sample temperature of 675 F. was recorded.

Explosive Power Test The two sample compositions were subjected to a standard ballistic mortar test to determine their explosive power relative to that of TNT which is the standard of reference in the test. U.S. Bureau of Mines Bulletin 346 (1931), Physica-l Testing of Explosives, by C. E. Monroe and I. E. Tiifany.

In this test, a standard ballistic mortar is charged with a weighed sample of the explosive composition. The mortar is suspended as a pendulum. Detonation is effected by means of a No. 8 blasting cap. Reaction yforces from the detonation cause a pendulum swing which is related to the explosive power of the composition being tested. The pendulum swing value for TNT is reported as percent.

The sensitive composition (having 2 percent by weight of No. 2 fuel oil) recorded a value on the ballistic mortar test of 94 percent. The power composition (having 6 percent by weight of No. 2 fuel oil) recorded a value of 123 percent.

The corresponding value for 40 percent dynamite is 90 percent; for 68 percent dynamite, the value is 105 percent.

Thus the present power explosive composition has an explosive power potential in the standard ballistic mortar test which is superior to 40 percent dynamite, to 60 percent dynamite and to TNT. Nevertheless, the present composition, by all standard detonation hazard tests, does not even behave as an explosive.

A further ballistic mortar test was carried out with an explosive composition containing ammonium nitrate prills having 0.3 percent by weight of inely `divided synthetic calcium silicate as a surface coating. The coated prills were homogeneously mixed with 4 percent by weight of No. 2 fuel oil. The ballistic mortar value for this composition was percent.

To illustrate the preferred embodiment of the present invention, FIGURE 3 is a cross-section sketch of a blast hole charged with explosive composition.

As shown in FIGURE 3, a blast hole 10 is provided in a rock strata 11. A container 12, preferably a moisture-proof bag, is placed in the blast hole 10. The container 12 is filled with the sensitive explosive composition of this invention, i.e., ammonium nitrate prills coated with 0.1 to 0.6 (preferably 0.25 to 0.40) percent by weight of iinely divided inert solids homogeneously adrnxed with 0.5 to 3.5 percent (preferably about 2 percent) of liquid hydrocarbons. The container 12 is armed by providing multiple wraps 14 of high velocity detonating fuse 13 in detonating relation therewith, preferably about the waist of the container 12. The detonating fuse -13 extends upwardly through the blast hole 10 above the ground surface to an initiation point 15, Where means, such as a blasting cap, are provided for initiating detonation of the fuse 13. The container 12 may be lowered into the blast hole 10 by means of the detonating fuse 13 tied thereto in multiple wraps 14.

The container 12 of sensitive composition, armed with multiple wraps 14 of detonating fuse is illustrated in FIGURE 3 at the bottom of the blast hole 10. In some instances it may be preferred to place the sensitive composition at the top of the explosive charge or intermediate of the top and bottom.

Additional containers 16, filled with the power composition of this invention (containing from about 4 to 8 percent liquid hydrocarbon) are placed in the blast hole 10 in bag-tobag contact with one another and in bag-tobag contact with the armed container 12. The entire explosive charge is confined in the blast hole 10 by means of stemming material 17, such as stones, earth, sticks and like materials.

The charge is detonated by initiating detonation in the high velocity detonating fuse 13. The resulting explosion 4front will travel along the fuse 13 into the blast hole 10, past the containers 16 of power explosive composition to the armed container 12 filled with sensitive composition. The plural wraps 14 of detonating fuse will effect detonation of the sensitive composition. Detonation of the sensitive composition in the container 12 will effect detonation of the power composition in the containers 16, resulting in a powerful blast.

By employing a light weight detonating fuse, preferably between 40-grains and 100-grains of PETN (or equivalent) per foot of length, the quantity of fixed explosive in the blasting system can be minimized.

The weight of detonating fuse required for detonation of the sensitive composition can be determined from the curve C of FIGURE l. Since the curve C represents 50 percent detonation reliability, some excess of detonating fuse weight should be provided as an assurance factor. Weights of detonating fuse are additive. Five wraps of 40-grain detonating fuse will provide the equivalent of ZOO-grains per foot of circumference. Three wraps of 60-grain detonating fuse will provide the equivalent of ISO-grains per foot of circumference. Provision of about 15G-grains or more per foot of circumference conveniently will provide a reliable detonation. rFrom the standpoint of safty and cost, the light weight detonating fuse is preferred.

Fuse-induced detonation occurs in the region of the fuse wraps 14, i.e.,in detonating relation with the sensitive composition. Misfires are virtually completely avoided. However, in the event of misfire, shovel operators can safely dig out the subsequently broken rock strata without fear that shovel impact might set off the undetonated charge. There is a complete absence of fixed explosives in the system except for the length of light weight detonating fuse.

Preferably the sensitive composition is provided in a moisture-proof bag to prevent misfires in water-filled or moist blast holes. Where dry blast holes are assured, the container need not be moisture-proof. The power explosive containers preferably should be moisture-proof for use in moist blast holes. Since water frequently is encountered only as an accumulation in the bottom of a blast hole, frequently only the bottom container requires moisture-proof construction. If desired, one or more containers of power composition may be opened and their contents poured directly into the blast hole as a freefiowing material. In dry blast holes, some sensitive composition also may be poured into the hole as a freeliowing material. For convenience and reliability, however, a container is preferred.

Using the explosive composition of this invention, successful blasting has been conducted in S-inch diameter blast holes containing about l0 bags of explosives, each weighing about 45 pounds. The composition has been successfully used in blasting 3-inch diameter holes in limestone quarries. One-inch diameter charges of the present explosive composition have been detonated.

Example.-Two explosive compositions were prepared from non-lustrous, relatively porous, friable ammonium nitrate prills coated only with 0.4 percent by weight of powdered diatomaceous earth. The first composition (sensitive composition) consisted of the described coated prills homogeneously admixed with 2 percent of No. 2 fuel oil. The second composition (power composition) consisted of the described coated prills homogeneously admixed with 6 percent of No. 2 fuel oil.

An 8-inch diameter vertical blast hole was prepared in a rock strata. A cylindrical burlap bag was filled with 45 pounds of the sensitive composition. Six wraps of 50- grain high velocity detonating fuse (filled with PETN) were tied around the bag which was then lowered into the vertical blast hole by means of the extending length of fuse. Seven cylindrical burlap bags were each filled with about 45 pounds of the power composition and dropped one by one into the vertical blast hole past the extending length of fuse. Stemming material (rocks and earth) was poured into the open top portion of the blast hole.

The extending fuse was detonated by means of a blasting cap. A powerful blast resulted in the rock strata producing effective shattering of the rock.

According to the provisions of the patent statutes, I have explained the principle, preferred construction, and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

l. The method for generating an explosion which comprises coating the surface of prilled ammonium nitrate with 0.1 to 0.6 percent by weight of nely divided inert solids and thereafter homogeneously admixing therewith from 0.5 to 8 percent by weight of liquid hydrocarbons, confining an explosive charge consisting essentially of the resulting admixture in contact with a high velocity detonating fuse which extends beyond confinement, said explosive charge Ibeing free of any ingredient that is per se sensitive to detonation by high velocity detonating fuse, and detonating said high velocity detonating fuse to `detonate said charge.

2. An explosive system consisting essentially of two confined explosive charges and a high velocity detonating fuse, the first of said charges consisting essentially of prilled ammonium nitrate containing as a surface coating from 0.1 to 0.6 percent by Weight of finely divided inert solids and being homogeneously admixed with 0.5 to 3.5 percent by weight of liquid hydrocarbons, the second of said charges consisting essentially of prilled ammonium nitrate containing as a surface coating from 0.1 to 0.6 percent by weight of finely divided inert solids and being homogeneously admixed with 4 to 8 percent by Weight of liquid hydrocarbons, said first charge and said -second charge being free from any ingredient that is per se sensitive to de-tonation by a high velocity detonating fuse, said first charge being positioned in detonating relation with said second charge, said bigh velocity `detonating fuse being positioned in `detonating relation with said first charge and extending out of confinement to initiating point, and means for initiating deto nation of said ydetonating fuse.

3. An explosive system consisting essentially of two confined explosive charges and a high velocity detonating fuse, the first of said charges consisting essentially of prilled ammonium nitrate containing as a surface coating from 0.1 to 0.6 percent by weight of finely divided inert solids and being homogeneously admixed with 0.5 to 3.5 percent by weight of liquid hydrocarbons, the second of said charges consisting essentially of prilled ammonium nitrate containing as a surface coating from 0.1 to 0.6 percent by weight of finely divided inert solids and being homogeneously admixed with 4 to 8 percent by weight of liquid hydrocarbons, said first charge and said second charge being free from any ingredient that is per se sensitive to detonation by a high velocity detonating fuse, said first ycharge being in detonating relation with said second charge, said high velocity detonating fuse being in contact with each of said charges, and extending out of confinement to an initiating point, said detonating fuse having a substantially uniform concentration of fixed explosive equivalent to less than References Cited in the le of this patent UNITED STATES PATENTS 2,069,612 Kir'st er ai. Feb. 2, 1937 10 1@ Horn et a1 Feb. 19, 1952 Lee et a1. Mar. 8, 1955 Sweetman May 17, 1955 Hradel et al June 30, 1959 Kolbe Sept. 15, 1959 FOREIGN PATENTS Germany Feb. 9, 1937 

0.1 TO 0.6 PERCENT BY WEIGHT OF FINELY DIVIDED INERT SOLIDS AND BEING HOMOGENEOUSLY ADMIXED WIOTH 4 TO 8 PERCENT BY WEIGHT OF LIQUID HYDROCARBONS, SAID FIRST CHARGE AND SAID SECOND CHARGE BEING FREE FROM ANY INGREDIENT THAT IS PER SE SENSITIVE TO DETONATION BY A HIGH VELOCITY DETONATING FUSE, SAID FIRST CHARGE BEING POSITIONED IN DETONATING RELATION WITH SAID SECOND CHARGE, SAID HIGH VELOCITY DETONATING FUSE BEING POSITIONED IN DETONATING RELATION WITH SAID FIRST CHARGE AND EXTENDING OUT OF CONFINEMENT TO INITIATING POINT, AND MEANS FOR INTIATING DETOMATION OF SAID DETONATING FUSE.
 2. AN EXPLOSIVE SYSTEM CONSISTING ESSENTIALLY OF TWO CONFINDE EXPLOSIVE CHARGES AND A HIGH VELOCITY DETONATING FUSE, THE FIRST OF SAID CHARGES CONSISTING ESSENTIALLY OF PRILLED AMMONIUM NITRATE CONTAINING AS A SURFACE COATING FROM 0.1 TO 0.6 PERCENT BY WEIGHT OF FINELY DIVIDED INERT SOLIDS AND BEING HOMOGENEOUSLY ADMIXED WITH 0.5 TO 3.5 PERCENT BY WEIGHT OF LIQUID HYDROCARBONS THE SECOND OF SAID CHARGES CONSISTING ESSENTIALLY OF PRILLED AMMONIUM NITRATE CONTAINING AS A SURFACE COATING FROM 